Emergency department patients at low to moderate risk for Acute Coronary Syndrome (ACS) make up about 50% of all those arriving at hospital emergency departments with chest pain, shortness of breath, or analogous symptoms of ACS. The cardiac-specific thin filament troponins have become the preferred biomarkers for use in the diagnosis of ACS because of their high sensitivity and specificity for myocyte necrosis. However, the relatively slow release of troponins from disintegrating myocytes, and the test imprecision and biological variation associated with low plasma levels require serial measurements to confirm diagnostic significance. Two clinical studies (one prospective, one retrospective) measured fracCRP, Troponin I (TnI), and the fracCRPxTnI metric on 210 such patients (105 each with final diagnoses of ACS negative or ACS positive), utilizing the phosphorycholine-capture, size exclusion HPLC method (Kiefer et al., Clinica Chimica Acta 413:1536-1541 (2012)). Overall, the method demonstrated strong diagnostic rule-in value for these patients on arrival, with a specificity of 96.2%, positive predictive value of 91.7%, sensitivity of 41.9%, and negative predictive value of 62.3%.